Automatic posting???

I know that this may be an HTML question, but, I have a form that needs to function in 2 parts. Part one: the user fills out the form, and then the form is sent to a processing page where it is broken up and verified, Part two: some of the information will be sent to Authorize.net for CC processing.... and then all information will be sent to the database. I need to know how to automatically send the information via post when im done with the insertion... This is basically 2 forms combined. doing different things, but I want to make PHP do everything at once. Is there a way to link a submit button to two different forms?